1. Field of the Invention
This invention relates to computer systems and, more particularly, to microprocessor power supplies.
2. Description of the Related Art
Modem microprocessors typically require high currents at low operating voltages. One type of power supply capable of providing such characteristics is a multi-phased or sequential power converter. The sequential converter uses multiple switching stages, where each stage may provide a portion of the load current during a particular active portion of the duty cycle. The stages are switched sequentially by control logic, which may ensure that the duty cycle of each stage is closely matched and thus that the load current is balanced among the stages.
However, this type of converter design may become complex and expensive as the input to output voltage differential increases and the output current requirement increases. This complexity may be due to the necessity of additional phases and the balancing of the load current.
One requirement for a microprocessor power supply may be to provide power in an efficient manner. Another requirement may be for the power supply to have a fast transient response. However, for a power supply to provide a fast transient response, the power supply may be required to provide peak output currents which are high enough to suppress voltage transients at the power supply output. To provide sufficient peak output current during a transient, it may be necessary to choose components that allow higher peak output currents. These higher peak output currents may cause higher reflected input currents. Therefore, power supply efficiency may suffer due to higher power losses associated with higher root mean square (RMS) input currents.
Various embodiments of an asymmetric multi-converter power supply are disclosed which include a first converter and a second converter coupled to provide power to an output node. In one particular embodiment, a control circuit is coupled to the second converter and is configured to selectively enable the second converter depending upon a voltage at the output node. The control circuit may be configured to enable the second converter only in response to determining that the voltage at the output node is not within a predetermined range. In one particular implementation, the second converter is configured to provide the power in response to one or more transient voltage events at the output node. Additionally, the second converter is characterized by a transient response time that is faster than a transient response time of the first converter, which is configured to provide the power in a steady state.
In another embodiment of an asymmetric multi-converter power supply, a first converter and a second converter are configured to provide power to an output node. The first converter is configured to provide power through a first series inductor. The second converter is configured to provide power to the output node through a second series inductor. The second series inductor has a smaller inductance than the first series inductor. Additionally, a control circuit is coupled to the second converter and is configured to selectively enable the second converter depending upon a voltage at the output node.